In-ear, behind-the-ear, over-the-ear/ear loop/on-the-ear, over-the-head, backwear/behind-the-neck headsets or the like, throat- and head microphones, earphones, and other voice communication devices are generally well-known in the art and used to facilitate one- or two-way communication between a user and another distant user or device. The voice communication devices or the like may be coupled to a mobile terminal that transmits and receives audio signals to and from the voice communication devices or the like via a wired or wireless communication channel.
During normal operation, a housing portion of the headset or voice communication device, etc. is fitted appropriately on the user's head, e.g. in the ear (canal), behind the ear, onto the ear or onto the nose, head, chin, etc. This housing portion often comprises a loudspeaker or similar, when worn in connection with the ear, coupled to a sound outlet of the housing portion so that audio signals received from the distant user or device are processed and transmitted to the user's ear canal, or more specifically to an ear canal volume residing in front of a tympanic membrane or eardrum.
For transmission of the user's own voice, an important type of headsets, voice communication device, etc. are adapted to pick up the user's voice by sound transmission via vibration through the user's tissue and/or bone structures. The voice pick-up may be enabled by a bone conduction microphone in vibratory contact with tissue of the user's head. A distinctive advantage of this type of sound pick up is good suppression of environmental noise in the microphone signal to be transmitted to the distant user or device allowing the user's speech to be conveyed with high fidelity and intelligibility even when the user is located in a very noisy acoustical environment. A further advantage is also the avoidance of a boom microphone or similar that needs to be located precisely in front of the mouth, is susceptible to picking up noise in addition to the user's speech, is uncomfortable and/or in the way of other equipment such as helmets, gasmasks etc.
Such bone conduction microphones are also referred to as bone conduction transducers, vibration pick-ups or transducers, etc.
FIG. 2 illustrates one example of a traditional bone conduction microphone (BCM) 101 that generally comprises housing 102 with an abutment or contact part 103.
The abutment or contact part 103 (forth only referred to as abutment part) is for abutment against and in contact with tissue of the head of the user, e.g. tissue in the ear canal of a user, and this part 103 is, during use, normally pressed or secured against at least a part of the head of the user and registers the vibrations propagating through the user's tissue and/or bone structures where the vibrations primarily are caused by the user speaking. A part, different from the abutment part, of the housing is generally for connecting/interfacing with the rest of a voice communication device or circuit (see e.g. 100 in FIG. 1) and is typically embedded in or connected to the device.
During use, a traditional BCM will be placed firmly against the ear or another suitable part of the user's head enabling good sound/vibration pickup properties.
However, such traditional BCMs, even when firmly in place, may still register unwanted vibrations and/or noise from the environment.
Even if the BCM is embedded in the tissue of the user to a certain degree, the BCM may still register vibrations or sound from the surrounding environment via air being in contact with the sides of the BCM.
In particular if the BCM is located on a more exposed location of the user's head e.g. like the nose, the neck, on the top of the head, the chin, behind the ear, in the ear (but outside the ear canal) etc.
As indicated in FIG. 2, a distal direction and an opposite proximal direction are defined in reference to the BCM, as shown by the two opposite arrows, where the sides of the BCM are located rotationally about the distal and proximal directions.
The distal end is labelled so since this is the end normally further/furthest away from the voice communication device that the BCM is mounted or attached to while the proximal end is labelled so since this is the end normally closest to the voice communication device.
A BCM is usually designed to register sound through vibrations from the distal relatively flat or curved abutment end or part. However, the sides of the BCM can potentially cause registration of unwanted vibrations and/or noise, which may degrade or mask the sound quality of the speech picked up from the user.
Patent specification U.S. Pat. No. 8,705,787 discloses a custom in-ear headset comprising a bone conduction microphone where the headset comprises a number of substantially hard ridges circumscribing a housing portion of the headset. The one or more ridges acoustically seals off a user's ear canal when the headset in inserted into the ear of a user and the ridge(s) thereby is/are pressed against a relatively soft cartilaginous portion of the user's ear canal.
Patent application WO 2014/022359 discloses earphone systems and methods for automatically directing ambient sound to an earphone device where an earphone device is to be inserted into the ear canal of a user. The earphone device comprises a sealing section that occludes the ear canal and an ear canal microphone that is acoustically coupled to the occluded ear canal via an acoustic tube.
Thus it would be a benefit to have a BCM or similar that does not register unwanted vibrations and/or noise or at least register unwanted vibrations and/or noise to a lesser extent.